can't load .so/.DLL - undefined symbol

Henning Thielemann lemming at
Mon Mar 17 14:33:50 UTC 2014

Am 17.03.2014 10:22, schrieb Simon Marlow:
> On 11/03/2014 22:11, Henning Thielemann wrote:
>> I am trying to understand the following linker message. I have started
>> GHCi, loaded a program and try to run it:
>> Main> main
>> ...
>> Loading package poll-0.0 ... linking ... done.
>> Loading package alsa-seq- ... can't load .so/.DLL for:
>> /var/cabal/lib/x86_64-linux-ghc-
>> (/var/cabal/lib/x86_64-linux-ghc-
>> undefined symbol:
>> alsazmseqzm0zi6zi0zi3_SystemziPosixziPoll_zdfStorableFd_closure)
>> I assume that GHCi wants to say the following: The instance Storable Fd
>> defined in module System.Posix.Poll cannot be found in the shared object
>> file of the alsa-seq package. That's certainly true because that module
>> is in the package 'poll' and not in 'alsa-seq'. But 'alsa-seq' imports
>> 'poll'. What might be the problem?
> It seems to have the idea that System.Posix.Poll is part of the alsa-seq
> package.  Perhaps you have a copy of that module on the search path
> somewhere, or inside the alsa-seq package?

This would confirm how I understood the linker message. Then I guess 
that compiling all packages at once in a single build dir with cabal was 
the problem. The command line was like:

$ cabal install --builddir=/tmp/dist --with-ghc=ghc7.8.0.20140228 poll 
alsa-seq pkg1 pkg2 pkg3 ...

After compiling the packages separately the problem has gone.

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